Speaker
Description
Recent measurements of the global spin polarization of $\Lambda$ hyperons further indicate the presence of strong vorticity of the rotating QGP and manifest the relativistic Barnett effect at the subatomic scale. Nevertheless, the related spin alignment phenomena of vector mesons and local spin polarization, especially in proton-nucleus collisions, cannot be simply explained by the vorticity as the late-time effect with the underlying equilibrium assumption for the spin degrees of freedom of hadrons or strange quarks. We review recent progress in spin transport phenomena in high-energy nuclear collisions, focusing instead on the early-time and non-equilibrium effects that extend beyond standard thermal-equilibrium frameworks. We introduce quantum kinetic theory as a microscopic framework for tracking non-equilibrium spin dynamics of quarks and hadrons, highlighting its key applications. In particular, we examine how non-equilibrium, overpopulated gluons in the early stages influence both the spin alignment of vector mesons—via quark–antiquark spin correlations during coalescence—and the local spin polarization of $\Lambda$ hyperons. We may further discuss non-equilibrium $\Lambda$ polarization induced by a rotating pion gas, with potential applications to intermediate- and low-energy heavy-ion collisions.